U.S. patent number 4,772,634 [Application Number 06/892,246] was granted by the patent office on 1988-09-20 for apparatus and method for methanol production using a fuel cell to regulate the gas composition entering the methanol synthesizer.
This patent grant is currently assigned to Energy Research Corporation. Invention is credited to Mohammad Farooque.
United States Patent |
4,772,634 |
Farooque |
September 20, 1988 |
**Please see images for:
( Certificate of Correction ) ** |
Apparatus and method for methanol production using a fuel cell to
regulate the gas composition entering the methanol synthesizer
Abstract
Methanol production is realized by utilizing a fuel cell to
control the gas composition of the synthesis gas stream being fed
to the methanol synthesizer.
Inventors: |
Farooque; Mohammad (Huntington,
CT) |
Assignee: |
Energy Research Corporation
(Danbury, CT)
|
Family
ID: |
25399632 |
Appl.
No.: |
06/892,246 |
Filed: |
July 31, 1986 |
Current U.S.
Class: |
518/704; 422/627;
429/478; 429/500; 429/425 |
Current CPC
Class: |
H01M
8/0612 (20130101); C07C 29/1516 (20130101); C07C
29/1516 (20130101); C07C 31/04 (20130101); Y02E
60/50 (20130101); Y02P 70/50 (20151101) |
Current International
Class: |
C07C
29/00 (20060101); C07C 29/151 (20060101); H01M
8/06 (20060101); C07C 027/06 (); B01J 008/00 () |
Field of
Search: |
;518/704 ;422/187-189
;429/17-19 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Richman; Barry S.
Assistant Examiner: McMahon; Timothy M.
Attorney, Agent or Firm: Robin, Blecker & Daley
Claims
What is claimed is:
1. Apparatus for methanol production comprising:
means for receiving a hydrocarbon feed and for producing therefrom
a synthesizer feed gas containing hydrogen, carbon dioxide and
carbon monoxide;
fuel cell means following said reformer means for receiving the
synthesizer feed gas from said reformer means and for consuming as
fuel a preselected portion of the hydrogen in the synthesizer feed
gas to realize a desired value for the stoichiometric number of the
synthesizer feed gas;
and methanol synthesis means following said fuel cell means for
receiving the synthesizer feed gas from said fuel cell means and
for producing methanol gas therefrom
2. Apparatus in accordance with claim 1 wherein:
said fuel cell means is a phosphoric acid fuel cell.
3. Apparatus in accordance with claim 1 wherein:
said fuel cell means is a molten carbonate fuel cell, said fuel
cell consuming as fuel as a preselected portion of the hydrogen in
the synthesizer feed gas and adding carbon dioxide to the
synthesizer feed gas upon passage of the synthesizer feed gas
through said cell to realize a desired value for the stoichiometric
number of the synthesizer feed gas.
4. Apparatus in accordance with claim 1 further comprising:
a variable load drawing current from said fuel cell means;
and means for adjusting said load so that the current drawn results
in the consumption of a preselected portion of the hydrogen
gas.
5. Apparatus in accordance with claim 1 wherein:
said fuel cell means is a molten carbonate fuel cell, said fuel
cell consuming as fuel a preselected portion of the hydrogen in the
synthesizer feed gas or adding carbon dioxide to the synthesizer
feed gas upon passage of the synthesizer feed gas through said cell
to realize a desired value for the stoichiometric number of the
synthesizer feed gas.
6. A method of producing methanol comprising:
reforming a hydrocarbon feed to produce a synthesizer feed gas
containing hydrogen, carbon dioxide and carbon monoxide;
consuming a preselected portion of the hydrogen in the synthesizer
feed gas by passing the synthesizer feed gas through a fuel cell
which utilizes a preselected portion of hydrogen in the synthesizer
feed gas as fuel;
processing the synthesizer feed gas after passage through said fuel
cell to produce methanol from the synthesizer feed gas.
7. A method in accordance with claim 6 wherein:
said fuel cell is a phosphoric acid fuel cell.
8. A method in accordance with claim 6 wherein:
said fuel cell is a molten carbonate fuel cell, said fuel cell
adding carbon dioxide to the synthesizer feed gas upon passage of
the synthesizer feed gas through said cell.
9. A method in accordance with claim 6 further comprising:
adjusting a variable load fed by said fuel cell to cause said fuel
cell to consume a preselected amount of hydrogen.
10. A method in accordance with claim 6 wherein:
the preselected portion of hydrogen consumed in said consuming step
in such as to realize a desired value for the stoichiometric number
of the synthesizer feed gas.
11. Method in accordance with claim 10 wherein:
said stoichiometric number is about 2.
Description
BACKGROUND OF THE INVENTION
This a method and apparatus for producing methanol and, in
particular, to a method and apparatus for producing methanol using
a synthesis gas.
In present day methanol production, the low pressure methanol
synthesis process (50-100 atm.; 200.degree.-300.degree. C.),
available since the 1960's, is universally favored over the high
pressure process (250-350 atm.; 350.degree.-450.degree. C.). In the
low pressure porcess, a feedstock having hydrocarbon content, e.g.,
natural gas, coal, heavy oils, naptha, propane or butane, is first
reformed to produce a gas stream rich in hydrogen. This
hydrogen-rich gas stream is then adjusted in composition and the
resultant stream containing hydrogen, carbon dioxide and carbon
monoxide catalytically synthesized to produce the desired
methanol.
Usually, the reformation process results in a synthesis gas whose
hydrogen content is greater than that needed for the methanol
reaction. This excess hydrogen may be used as fuel in the plant or
may be cryogenically separated from the synthesis gas stream and
used in other applications. Also, CO.sub.2 may be added to the
synthesis gas stream to convert some of the hydrogen to CO. This
procedure adjusts the stoichiometric number expressed by equation
(a) below to the desired value, ##EQU1## thereby increasing the
methanol yield. However, the CO.sub.2 added to the gas stream is
generally recovered from the reformer flue which is a costly
process.
While the above procedures have thus been successfully utilized for
methanol production, other procedures which could result in reduced
cost are still being sought.
It is, therefore, an object of the present invention to provide an
apparatus and method for methanol production.
It is a further object of the present invention to provide a method
and apparatus for methanol production utilizing unique means for
adjusting the hydrogen content of the synthesis gas.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention the
above and other objectives are realized by passing the
hydrogen-rich synthesis gas through a fuel cell which is adapted to
add a preselected quantity of CO.sub.2 to the gas stream and/or
consume a preselected portion of the hydrogen in the gas stream as
fuel gas. The gas stream with reduced hydrogen content and its
stoichiometric number adjusted to the desired value is then fed to
a methanol synthesizer which forms methanol from the gas stream
products.
With the present invention, the hydrogen consumed in the fuel cell
is readily adjusted and controlled by adjusting the load and,
therefore, the current of the cell. As a result, the composition or
makeup of the gas stream leaving the cell can be precisely adjusted
and controlled so as to provide a gas stream for the synthesizer
having the desired stoichiometric number. Also, the electrical
output of the fuel cell can be used as an electrical energy source
so that the hydrogen removal process is carried out in a manner
which results in maximum usage of energy.
BRIEF DESCRIPTION OF THE DRAWING
The above and other features and aspects of the present invention
will become more apparent upon reading the following detailed
description in conjunction with the accompanying drawings in which
the sole FIGURE illustrates a system for producing methanol in
accordance with the principles of the present invention.
DETAILED DESCRIPTION
In the FIGURE, hydrocarbon feedstock, shown as natural gas, is fed
into a reformer 2 which converts the feedstock into a gas stream 3
which is rich in hydrogen and which also contains carbon dioxide,
carbon monoxide and unreacted methane. The reformer 2 may be a
conventional steam reformer or gasifier, depending upon the
hydrocarbon feedstock.
The gas stream 3 is then fed into a fuel cell 4 which drives a
variable load 5. A portion of the hydrogen in the stream 3 is
utilized as fuel by the fuel cell 4 and/or CO.sub.2 is added to the
stream by the fuel cell, so that the stream 3 passes from the fuel
cell 4 with an increased CO.sub.2 content and/or a reduction in its
hydrogen content.
The stream 3 is then coupled into a conventional methanol
synthesizer 6 wherein the stream is converted into methanol. As
shown, synthesizer 6 includes a syn-gas compressor 6a which
receives the stream 3 from the fuel cell 4. The output of the
compressor 6a is coupled to a recycle compressor 6b and from the
compressor 6b to a methanol synthesis unit 6c.
The output of the unit 6c is coupled to a separation apparatus 6d
which separates the produced methanol from the other constituents
in the unit 6c output. The separated methanol is then passed to a
distillation unit 6e and from there out of the synthesizer 6.
Portions of the other constituents (hydrogen and CH.sub.4) in the
unit 6c output are re-cycled back to the reformer 2 and the
re-cycle compressor 6b, respectively. Added to the former portion
is an additional output of the separation unit.
As can be appreciated, by controlling the current drawn from the
fuel cell 4 with the variable load 5, the gas composition of the
stream 3 as it leaves the fuel cell 4 can be precisely controlled.
As a result, the stoichiometric number of the stream 3 fed to the
synthesizer 6 can also be precisely controlled to that desired for
the methanol synthesis process. In the FIGURE, typical compositions
of the gas stream 3 entering and exiting the fuel cell 4 are shown
for realizing a stoichiometric number of about 2, which is desired
for methanol processing in synthesizer 6.
The fuel cell 4 can be a phosphoric acid fuel cell in which case
about twenty-five percent of the hydrogen in the gas stream 3 can
be consumed to provide the above-mentioned stoichiometric number.
In such case, a 104 MW size phosphoric acid fuel cell will be
required for a 3000 ton/day methanol plant.
The fuel cell 4 may also be a molten carbonate fuel cell. With this
type of cell, hydrogen is removed and CO.sub.2 is simultaneously
added to the stream 3, as the stream passes through the cell. The
addition of each molecule of CO.sub.2 to the stream is equivalent
to the consumption or removal of two hydrogen molecules. As a
result, less hydrogen molecules need to be consumed by the cell 4
to realize the same stoichiometric number. This, in turn, allows
more hydrogen to be in the stream 3 entering the synthesizer 6 and,
as a result, more methanol to be produced.
In all cases, it is understood that the above-identified
arrangements are merely illustrative of the many possible specific
embodiments which represent applications of the present invention.
Numerous and varied other arrangements can readily be devised in
accordance with the principles of the present invention without
departing from the spirit and scope of the invention.
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